Committee Chairman Patrick J. Leahy, Vermont Democrat, invited former Rep. Gabrielle Gifford’s husband, Mark Kelly, among others, to testify for the other side. In his prepared remarks, Mr. LaPierre will say, “When it comes to the issue of background checks, let’s be honest: Background checks will never be ‘universal’ because criminals will never submit to them.”

Currently, a gun owner who goes to a retail shop to purchase a gun from a licensed dealer is subject to the National Instant Criminal Background Check System. The system, run by the FBI reviews criminal history, mental health and restraining-order records to weed out those who are legally barred from gun ownership.

The gun grabbers’ real goal has always been universal registration, and tracking every gun owner in the country would be a big step in that direction.

“The law already requires licensed gun dealers to run background checks, and over the last 14 years that’s kept 1.5 million of the wrong people from getting their hands on a gun,” said Mr. Obama, when he announced his gun-violence task force results on Jan. 16. “But it’s hard to enforce that law when as many as 40 percent of all gun purchases are conducted without a background check.”